The Experimental Irradiation Core provides for the use of ionizing radiation for members of the University of Michigan Comprehensive Cancer Center. This facility is equipped to perform moderate dose rate gamma irradiation (0.1-4 Gy/min) of cell cultures, tissue specimens, or animals as well as low dose rate irradiation (0.05-0.5 Gy/hr) of cell cultures. The core also maintains the 137 Cs irradiator in the spf facility of the Animal Core. Personnel within the core assist in the experimental design, dosimetry, and delivery of these forms of ionizing radiation They also maintain the safety and smooth operation of this facility through routine quality assurance procedures, calibrations, and preventative maintenance. This core provides a unique opportunity for Medical Campus investigators to have this service in a convenient location, since it is the only such facility on the Medical Campus. The specific goals of the Irradiation Core are to: Support studies in the radiation biology of moderate dose rate irradiation of cell cultures and small animals, such as mice, rats, and rabbits. Permit the study of low dose rate irradiation in cell culture. Provide irradiation services for investigators whose primary interests are not in radiation biology, but who need this tool in support of other efforts (for example, immunosuppression of animals prior to stem cell transplantation through total body irradiation).